Combustion control apparatus



APril 8, 1952 D. M. BORDEN ET AL 2,592,385

COMBUSTION CONTROL APPARATUS Filed May 2'7, 1949 3 Sheets-Sheet l um vaC'plni'ra Z Bax BY 7% 444, 1M

FTTZFIVE/SZ P 8, 1952 D. M. BORDEN ETAL 2,592,385

COMBUSTION CONTROL APPARATUS Filed May 27, 1949 s Sheets-Sheet 2 April1952 D. M. BORDEN ET AL COMBUSTION CONTROL APPARATUS 3 Sheets-Sheet 3Filed May 27. 1949 TNVEN Patented Apr. 8, 1952 COMBUSTION CONTROLAPPARATUS David. M. Borden, Huntington Woods, and Paul T. Nims, Detroit,Mich., assignors to Chrysler Corporation, Highland Park, Mioh., acorporation of Delaware Application May 27, 1949, Serial No. 95,654

18 Claims.

This invention relates to combustion regulating apparatus, particularlyapparatus controlling the process of combustion in a burner of which thefuel supply is regulated according to predetermined rates dependent uponthe temperature of the ener y gases discharged.

In burner devices for machines of which the combustion characteristicmay be commonly referred to as the external type, certain problems arisewhich lead to complications not found in comparable equipment, forexample, internal combustion engines. In internal combustion engines theleanness or richness of the fuel mixture is not critical to the point ofeventually incapacitating the machinery in case of error since too richa mixture merely incurs the result that unburnt fuel for which there isinsu-fficient oxygen in the cylinders is merely discharged withoutapparent damage. On the other hand, in a burner such as involves anexternal combustion process the condition of too rich 2. mixture of fuelis attended by excessive temperatures which can rapidly cause thestructure to deteriorate and be permanently damaged. If the mixture isleaned up too drastically, then the danger arises that the fire in theburner will be blown out and lost altogether. To meet this added problemin such combustion devices as the latter, designers in the field haveturned to elements by means of which the combustion temperature may besensed and the fuel flow corrected in time to prevent loss of the flamealtogether in the burner as due to too lean a mixture or elseexcessively elevated temperatures such as may be due to an excessivelyrich mixture. A familiar technique among the known forms of controllingburners as to their combustion temperature is that of employing ametallic device such as a thermocouple for actually registering thetemperature of combustion. Certain disadvantages, however, reside in theuse of direct reading devices. For one thing, because of the poorresponse characteristics inherent in a system of temperature controldependent on the sensing of metal temperatures such a method has come tobe considered generally impracticable particularly in the event of hightemperatures existing in the burner. The sensing and control ofcombustion gas temperatures appears to be more advantageous than anattempt to control directly the temperature of the critical burnercomponent. The combustion gas temperatures method appears more practicalfor high temperature application and moreover is not affected by theerrors of radiation, conduction, and oxidization such as affectconventional gas temperaturesensing devices.

An object of the present invention resides in the provision of controlapparatus not dependent upon a direct reading temperature device in thepath of the combustion gases from a burner. According to this feature ofthe invention there is no need for continual calibration of any suchthermocouple device exposed to the deteriorating effects of gases havingan elevated temperature and moreover, the problems introduced owing toerrors in radiation, conduction, and oxidization of a thermocouple arerendered inconsequential.

Another object of the invention resides in the provision of electricalapparatus which when calibrated and set, is free from operating errorscontinually introduced by sediment deposits and the like such as areattendant with counterpart types of control apparatus which involvecalibration and adjustments for errors in valving.

A further object resides in the provision of electrical slider means ofwhich the friction characteristic is a minimum such as may be readilyoperated by pressure and temperature-sensitive control devices with aminimum loss as to the actuating forces available.

Still another object is to provide a control apparatus from which aseries of valves and restrictions may effectually be eliminated in orderto prevent a cascading of errors and in which each sensing device variesmore or less with its own error and not according to accumulative errorsof the associated sensing elements.

A still further object resides in the provision of metering valvesetting means in the form of a rapidly responsive electric motor adaptedby a suitable amplifier to respond to small electrical signals.

A yet further object resides in the provision of control apparatus bymeans of which combustion temperatures can be effectively controlled byinferential means such as are not necessarily exposed to excessive heatefiects for which present day materials and their uses are not adequate.

Other objects and advantages will be more particularly pointed outhereinafter or will become apparent as the description proceeds.

The instant invention takes advantage of certain fundamental relationswhich may be set up from a thermodynamic standpoint upon proper analysisof fuel combustion processes. As regards an isolated burner having acombustion zone it may be assumed first that the weight of the gasesentering the combustion zone is substantially equal to the weight of thegases leaving that combustion zone. Of benefit in making a more completeanalysis of the combustion process is the assumption of an upstreamstation No. 1 and a downstream station No. 2 on the respective sides ofa combustion zone at which stations the quality of the gases may beconceived of in 3 terms of the generally accepted symbols set forthbelow:

Station No. l

sl tlTlAl Station No. 2

Combustion PnQPtZTZ Z zone W2V2 Upstream Downstream At the upstream sideof the combustion zone, the static pressure (PS1), the total pressure(Pu) and the gas temperature (T1) are known. On the downstream side, thestatic pressure (PS2) and the total pressure (Pa) are known, while thegas temperature is unknown. The thermodynamic relationship between theseknown and unknown quantities may be established as follows. The notationto be used consists of:

A=cross sectional area c=specific heat at constant pressureg=acceleration of gravity J=mechanical equivalent of heat P=pressureT=temperature V=gas velocity W :gas Weight p=mass density of gas r=ratioof specific heats s=static t=total 1=upstream or cold point2==downstream or hot point 1 1 P 51 32 E FIZTQ Substituting, since W1=W2(approximately): K V1 z lzTn From (5) and (l):

o5 lea l Simplifying by using K5=(fi gf 1 lee l 4 An analysis ofEquation 8 reveals that for the temperatures and pressures involvedduring the normal range of operation, the exponent may be reasonablyaccurately evaluated as a decimal constant and certain other quantitieslikewise evaluated. Then by holding the quantity temporarily constant, aplot of Ta as y along the Y axis on coordinate paper against thevariable quantity as 9: along the X axis, yields a simple curve. Anotherreasonable operating value for quantity Changing the slope of the curvesof the plots of Equation 9 is accomplished simply by multiplying theright side by slope constant K6, which when united with the constant K5already in the equation, may be designated combined constant K.

Accordingly, for the practical range of values employed, the Equation 8may be reduced to:

PB 9 rsczrsr,

and Th is easily measured (13) a2(Pt2 a2) where T2 and T1 representrespectively the total temperature at station 2 and the totaltemperature at station 1.

Relations derived from fundamental Equation 8, such as Equation 13 andother modifications, will be seen to be used to advantage in the instantinvention. It is by means of these relations that the combustiontemperature of the burner ,may beinferentially determined and'br'oughtinto conformity with the combustion temperature actually desired by theoperator of the burner.

In the accompanying drawings in which like reference numerals are usedto designate similar parts throughout, there are diagrammaticallyillustrated suitable mechanical embodiments for the purpose ofdisclosing the invention. The drawings, however, are for the purpose ofillustration only and are not to be taken as limiting or restricting theinvention since it will be apparent to those skilled in the art thatvarious changes in the illustrated embodiments may be resorted towithout in any way exceeding the scope of the invention.

In the drawings:

Figure 1 is a longitudinal sectional view of a fuel system to which thecontrol apparatus of the instant invention has been applied;

Figure 2 is a schematic view of a control apparatus of Figure 1;

Figure 3 is a schematic view of a modified control apparatus; and

Figure 4 shows a further modification.

In particular regard to Figure 1 of the drawings, the control box Inconstructed according to the principles of the instant invention isshown applied to a controlled combustion system. A manual setting leverI8 is provided on box It to afford a means of setting the selectedoperating temperature for the combustion system. Into one side ofcontrol box [0 are fed signals from a sensitive device going to form aset comprised of a temperature responsive element 22, a total pressureresponsive element 24, and a static pressure responsive element 26.ditional set of sensing elements is provided for the control box, whichis comprised of a total pressure responsive element 32 and a staticpressure responsive element 34. The foregoing sets of sensitive elementsare adapted to be mounted in conjunction with a burner having a means 42forming an inlet passage for the air or other combustion-supportingmedium introduced into the burner. A structural member 44 serves toprovide a passage for the flow of the energy laden products ofcombustion of the burner being discharged from the combustion zone. Thecombustion-supporting medium is led through the inlet 42 along theinside of the walls 46 of the outer tube of the burner. Inwardly spacedfrom walls are walls 48 formed by a series of frustoconical elements 58,which are positioned to constitute an inner tube for the burner.Suitable brackets and clips 5| and 53 serve to position thefrustoconical elements 50 against displacement within the burner. Theair from the chamber between the respective outer and inner tubes is ledthrough the spaces between the frustoconical elements and directedinside the inner tube in a direction toward the closed end 52 thereof.Arranged through suitable openings in wall 52 are respectively a spraynozzle 54 served by a fuel inlet line 55 and an igniter 56 energized bya conductor 51. The fuel may ordinarily be introduced into the innertube in a suitable spray pattern by nozzle 54 and ignited by the device56 to burn in the presence of the turbulent air flow within the innertube. The products resulting from the combustion are led from the burnerin an energy laden state through the discharge outlet 44.

Control box l0 may be powered from a supply generally indicated at 66from which it derives energy that is translated into a fuel controlsignal and passed along a cable l9. Suitable valv- An ading at 70provides for fuel control to be exerted by the control box over theatomizing nozzle just described. The valving mechanism is provided witha metering orifice 12 which establishes communication between a chamber14 leading from the fuel supply line of the nozzle, to the bypasschamber 16. Valving I5 is adapted to be positioned within the meteringorifice 12 by means of a member 11 on which it is carried and to whichis connected a rack 18. The control signals emitted from the control boxthrough cable I9 may be fed into a motor of which the rotor 82 carries ashaft 86 therewith. A pinion 88 carried by the rotor and shaft 88 mesheswith the rack 18 to position metering valving (5. A suitable ground at84 may be provided for motor 80. The main fuel pump 90 is adapted toreceive fuel from the line 96 and introduces this fuel under pressureinto the supply line 55 for atomizing nozzle 54. The bypass of pump 90is arranged to be controlled by the metering motor 80 such that thequantity of fuel actually available for introduction into the burner maybe accurately controlled. Intake line 96 for pump 90 is itself suppliedfrom flow structure 92 provided with fuel by a line 98. Transfer pump 94serves the line 98 and is provided with a bypass valve 59 for regulatingthe operation thereof.

During normal operation of the combustion system just described, acontrolled supply of fuel is introduced into the inner tube 48 of theburner and there broken into small particles readily consumed in themixture of burning energy gases. The temperature and the pressures ofthe incoming relatively cooler air is registered by the sensing set 20and communicated to control box [0. The energy gases passing alongdischarge 44 may be expected to have a characteristic highly elevatedtemperature. Therefore only the static pressure and total pressure ofthe energy gases is conveniently registered by means of the sensing set39 and communicated to the control box l0. These data afforded by thesensing sets are sufficient of themselves to provide the control boxwith sufficient information to regulate the temperature of combustionaccurately by means of the metering control which the control boxeffectively exercises over metering valve 15.

In Figure 2 is schematically shown a system designed to control thenozzle box temperature T2 by action based on the values of the othervariables of Equation 13. The voltage level at point E7 is a continuousindication of temperature at the nozzle box.

This control system is unusual in that the required multiplication,division, and subtraction are accomplished automatically byelectromechanical means. The results of the computation, represented byvoltage level E7, is communicated to the operators temperature settinglever 18 and assembly to establish a balanced circuit. When, however,the lever I8 is moved to call for a temperature at the nozzle boxdifferent from that indicated by voltage level E1, an unbalance iscreated which is transmitted in modified electrical form as a signal toamplifier means and to fuel metering motor 85. The motor 80 then variesthe flow of fuel supplied to the burner to accord with the nozzle boxtemperature demanded and eventually a balance is struck again in thesystem. An examination of the detailed operation of the balancingcircuits is reserved to a later portion of the instant discussion.

In particular regard to the calculating means, the basic circuit is apositionable means in the form of a potentiometer connected to give anoutput voltage which is proportional to the product of the input voltageand slider position. If each slider is positioned by one of thepressures or temperatures in Equation 13 then the electrical circuitwill perform the necessary computation. The arrangement uses amplifiertubes in the cathode follower circuit to make the currents in thevarious potentiometers less dependent on one another.

The calculating means Ii may conveniently be divided into threeoperating portions I2, It, and I6. At the input side of portion i2, is aconductor I02 leading from the power supply 60, in series with apotentiometer I9 2. The slider of the potentiometer is carried by a barI06 pivoted at I93. The positioning means for the bar includes a rod Iiiattached to the free end of a temperature bellows IE2 which expands orcontracts in accordance with temperature changes sensed by the remotetemperature bulb or capsule 22. Bulb 22 is arranged on one end of asealed conduit communicating with bellows H2 and disposed in the inletair passage of the burner. Since the slider of the potentiometer variesits position with the temperature of the inlet air and taps mi fromlevel E'o at H32 a voltage proportional to the temperature, the voltagelevel E1 at point lilfivmay be related properly to the temperature bythe following equation:

(14) E1=T1Eo The cathode follower circuit H4 is used to impress thevoltage E1 onto potentiometer I It without adding a current drain topotentiometer I04. The slider of the potentiometer H6 is mounted in asimilar fashion on bar i it pivoted at I20, to take a position inrespect to the static pressure PS2 of the hot gases. Tapped off at pointI25 of vacuum bellows unit I25, the voltage E2 may be expressed inequation form as:

(15) E2=Ps2El As such, the voltage E2 is transmitted to operatingportion it. I

In regard to portion I 43, the voltage E2 is transmitted by conductorI28 to the slider on bar I38 pivoted at I 32. The bar swings along thepotentiometer dividing it into an upper segment I34 and a lower segmentI36. The lower segment E35 is connected to the paralleled low resistorI33 and high resistance primary winding I40. Bar I moves in response tothe static inlet pressure PS1 through the agency of vacuum bellows unit54 3. Hence the pressure i n is represented by the value of theelectrical resistance offered by segment I36. For all practicalpurposes, the current carried by segment its is all directed through thelow resistor I38 of resistance value R1. The voltage drops across theseresistors may be expressed in equation relationship as follows:

1 E R1 (16) z i1+ i The value of R1 is purposely chosen low relative toresistance PS1 such that equation may be transposed and reduced as:

F I i z' R132 11: 3 P81+R1 P81 3 The high resistance coil I w is theprimary winding of a transformer I45 Whose ratio is predetermined as Thesecondary M8 is connected to conductor I50 whose potential E4 bears thisrelation to the input voltage E32 Conductor 1 53 is connected to acathode follower circuit it? in such a manner as to renderthe output oftransformer I46 at zero.

The voltage E4 is impressed through potentiometer terminal 55 ontopotentiometer I56. The slider bar W8 is pivoted at Ito to provide atapped off potential E5. The value of E5 depends on the position of theslider, set in proportion to the difierential in pressure afforded by Pmover s2; that is to say, the velocity pressure at station 2. As thepressure in the lower bellows iiii rises relative to that of the upperor PS2 bellows I85, the voltage E5 approaches the impressed voltage atits, El. In other words:

This adjusted voltage, is transferred over to operating portion M.

In the operating portion It, connection I53 energized at the level ofE5, is carried by the end of slider bar Ilii which is pivoted at it?)and positioned in accordance with the Value of the velocity pressure atstation 1. The positioning mechanism includes a difierential rod H2controlled downwardly by the excess in pressure rise of the totalpressure Pu, transmitted to pressure bellows I'M, over static pressureP51, in bellows I15. The potentiometer for slider bar He is inverted inthe manner of the potentiometer for bar I33, explained above. Thepotential E's supplied to line I32 may be expressed by the followingrelation in which symbol R2 refers to the resistance ofiered by lowresistor i842 Since R2 is relatively low, Equation 21 can be simplifiedin the fashion of Equation 17.

Equations l4, 15, 19, and 20 results in an Equation 25 like thefundamental control equation number 13:

82 H an This potential is fed from the computing section II of controlbox I6 into the fuel motor controlling section [3.

As previously stated, the tube in each cathode follower circuit servesthe purpose of tapping oif voltages from the preceding potentiometerwithout taking current of consequence out of the slider of thatpotentiometer. Thus the follower circuit cannot by its own variancesintroduce an error in the calculation process of the precedingpotentiometer. Otherwise, the error in the first potentiometer I64 ofthe group would represent a cascading of variables in the succeedingpotentiometers, II6, I34, etc., and be nowhere near to allowable.Practically, it may be found desirable to install a cathode tube,similar to H4 and I52, between the operating portions I2 and I4, andanother between portions I4 and I6. The purpose in the one case would beto make the operation of potentiometer II6 entirely independent ofpotentiometer I36; in the other case, potentiometer I56 would be madeless dependent on potentiometer I86.

As to the controlling section I3, as a unit it operates to balance upthe voltage level of E as against that level in terms of temperaturesetting, called for and instituted by the manually set lever I8. Inequation form the relation may be expressed:

Wi=rate of fuel flow,

t=time, and

K y=constant for fuel system.

The mode of operation is a devious one whereby section I3 actuates thefuel metering motor 86 to change the rate of fuel flow and consequentlythe downstream temperature T2. The voltage level at E7 then changes tobalance out the temperature setting, Tsct, called for.

Potentiometer I98 is bridged across supply lines I94 and I95 so as to bein series with a calibration resistor I96. Temperature setting lever I8,grounded by the pivot I99 and its line 266 is mounted to slide along thepotentiometer I98. Line I92, at the voltage level of E7, connects withthe lever I8 and ground line 266 through a resistor 262. Any unbalancein the system is reflected by suitable signal owing to voltage drop orrise over this resistor 202 to ground line 266.

For providing D. C. power to the audio amplifier tube 226 and phasediscriminator tubes 236 and 246, conventional means may be provided suchas rectifier tube 256. The above tubes have a common terminal for theirgrounded heaters denoted by the character F and may be connectedthereby, in parallel, to one terminal of the secondary winding 266 oftransformer 266, similarly marked F. The plates of the rectifier tube266 may be connected to the transformer 266 at the terminals ofsecondary winding 268 seen to be grounded by center tap 269. On thecathode side of tube 256 is a filter 252 which delivers a steady D. C.supply to audio amplifier tube 226.

During balanced condition of the system, that is when the voltage E7 atline I92 is at the level of ground line 266 or ground level, the grid inamplifier tube 226 is uncharged and the tube conducts uninterruptedly.Associated with the plate circuit of tube 226 by a coupling condenser22I in line 222 are grids of phase discriminator tubes 236 and 246.These grids are grounded through a suitable resistance at point 223.During steady state conditions these grids accordingly will have neutralcharges and will allow the discriminator tubes 236 and 246 to conductsteadily. The cathodes of these discriminator tubes are grounded at 223and 243 respectively, the plate connections are led to the end terminalsof secondary winding 262 in transformer 266, each plate lead going tothe opposite end respectively. Winding 262 is provided with a center tap263 which is led over to field coil 86 grounded at 8'! and condenser 88in parallel, also grounded. This field coil is located in fuel meteringmotor 86 which comprises a rotor 82 and another field winding or coil 84disposed in a 96 relation to the field coil before mentioned. The motoris of two-phase type and is actuated by these two coils. Field coil 84is energized by power source 66 which also energizes the primary winding26I of the transformer 266. However, the interposition of condenser 85in series with the coil 84 causes a phase shift as between the voltagesover these respective coils 84 and 26I such that the voltage of winding84 leads the voltage of coil 26I by an angle The phase relation of coils26I and 262 is essentially the same. Hence the variance between thephase angles of the voltage of coil 262 and winding 84 is of the sameorder as As has been stated above, the charge on the grids of thediscriminator tubes normally is neutral. These tubes under thiscondition normally conduct alternately, that is, tube 236 will conductfor half the cycle through the upper half of coil 262 through motorwinding 86 and then tube 246 conducts for the second half of the cyclethrough the lower half of coil 262 through the center tap to the winding86. The condenser 88 serves in a flywheel capacity and tends to maintainan unwavering direct current fiow through winding 86 with the resultthat a steady flux is maintained in the field. Within the influence ofcoil 84 an alternating flux is maintained and the two fluxes do notprovide any field which actuates the fuel metering motor rotor 82. As tooperation of the system of the embodiment of Fig. 2, the firstindication of unbalanced activity will be that voltage E7 in line I92will attain a level alternately above and below the ground levelmaintained in line 266. Let it be assumed that the instantaneous chargeon the grid of tube 226 during the unbalanced state will be positive atthe same instant that the top terminal of coil 262 goes positive.Conduction in tube 226 is decreased and the input plate of condenser 22Igoes less negative with the result that the grids of tubes 236 and 246go positive. Since the upper terminal of coil 262 is positive, the uppertube 236 is the one which will conduct for this half cycle at astimulated production due to the change in the charge on the grid.Accordingly, the coil 66 has the effect of an increased field. Duringthe next half cycle, however, the charge on the grid of amplifier tube226 goes negative with the result that during this second half of thecycle when tube 246 conducts, the grid of tube 246 goes negative to theend that tube 246 conducts only a fraction of its steady state output.Hence, the flux in winding 86 dies down appreciably with the effect thatthe field of winding 86 has a pulsing action. As has been stated, thevoltages actuating windings 84 and 66 are disposed at an angle to oneanother and the windings themselves physically are disposed at an angleof Their fields tend to cooperate yielding a resultant which imparts arotating field to fuel motor 86. The more the grid charges are,relatively speaking, the greater the vector quantity of the resultantis, such that motor speed depends upon the amount of unbalance in thesystem. On the other hand, if the unbalance in the system over resistor202 is in the other direction the instantaneous charge on the grid inthe amplifier 220 will be negative at the same time that the upperterminal of coil 262 is itself positive. Under such condition the tube240 will conduct at a more stimulated pace while the conduction of tube238 will be retarded. The field produced by winding 86 will be growingand dying in an exact opposite relation to what it was during the firstsituation considered. Hence the rotating field will take the oppositedirection and the fuel motor will rotate in an opposite direction. Theshaft rotation then may be said to correspond in direction and magnitudewith the temperature error. Of significance in the overall operation isthis last mentioned fact that the greater is the unbalance created inthe system the greater is the field created and collapsed in winding 86and the stronger is the fuel motor response.

The embodiment shown in Figure 3 is arranged to operate from a modifiedcontrol equation. This modification is accomplished by substitutingdirectly in Equation 8 some actual values met over the normal range ofoperation, the remaining terms reducing to:

The equipment used is essentially the same as for the first embodiment,depending upon the same variables as formerly except employing them in aslightly diiferent manner. The layout of Figure 1 again applies.

The device of Figure 3 is different in some marked respects however. Thesole source of power relied on by the control box and the meteringequipment is of D. C. nature. The fuel metering motor is D. C. as well.Any alternating current required in the net is self-converted within thesystem by an oscillator incorporated therein. All the vacuum tubes andthe fuel control motor have the same direct current power source incommon. Metering motor Bil may be provided with two motor windings ofwhich one, when selectively energized, will cause motor rotation in onedirection whereas the other when selectively energized will cause motor80' to rotate in the other direction.

The control box It may be comprised of a computing section H and acontrolling section l3. Both sections may be furnished a supply ofalternating current by transformer 460. Supply line 392 to the computingsection is maintained as potential E which is alternately above andbelow the ground level at a value determined by the relative position ofthe grounded slide wire bar 18' relative to its potentiometer 398.

Line 362 is connected to the terminal of a potentiometer 3% whose otherterminal is served by return 3%. This potentiometer is the first of aseries of positionable potentiometers, including am and 33, each ofwhich is in parallel with the circuit of the slider of the respectivepreceding potentiometer. Every time a voltage is tapped off by one ofthese sliders, a step such as multiplication for instance, in thecomputation is performed. The mechanics involved are essentially as setfor in regard to the first embodiment described.

Slider bar 3% may be mounted on a pivot 301 and is adapted tocommunicate the voltage tapped off, by means of connection 308, toconductor 313. The voltage level in conductor M3, E1, may be expressedas: a=gfa where K1 is a correction factor for the system. Also: 31 E,=E,(173P.1- 149.21%

Equation 31 is transformed into a reality owing to the ratio of areasselected to be exposed in the bellows 322 and bellows 324. From anupstream station number 1, the static pressure registered by tube 26'may be transmitted to the outside surface of bellows 32 6. The totalpressure Pu is communicated to the inside of this bellows from Pitottube 2d. The inside of the top of bellows 324 however, is partiallyblanked oil to pressure Pu by a vacuum bellows 322 to the extent thatthe ratio of effective areas exposed to the actuating pressures are inthe ratio of 173 to 149.2 for the top outside and top insiderespectively. The net force acting in rod 320 depends then on thequantity (173Ps1-1492Pt1) Slider bar M8 is pivoted at 3H! and connectedat 326 to conductor 328.

Another subtraction transpires at positionable potentiometer 334 whichis actuated by the pressure differential between Ptz and PS2, orinversely to the velocity pressure at an upstream station number 2,whichever way is more suitable for the reader to look upon thesituation. Slider bar 358 is pivoted at 359 and there connected toconductor 366. A correction factor is necessary to be introduced at thiscomputation, and the following equation relating the level at 366, E3,to the level at 328, E2 may be derived:

Potentiometer 3'16, next in the circuit, is of different design from theprevious instruments. It is not only inverted as connected, but alsoconstructed to have a cubic taper winding. The static pressure signalfrom tube 26 operates to yield inversel to the cube of its own value,the voltage E4 in conductor 3%. It may be accordingly stated that:

Slider bar 3ft is pivoted at connection 368.

To complete the circuit between conductor 3M and return line 3&3 are tworesistors in series,

315 and 22. The resistance oifered at 375 is of high value R3. Theresistor 22', a temperature sensitive type located in the air inlet ofthe burner substantially as is the thermometer bulb of Figure 1, offersrelatively low resistance which varies directly with the totaltemperature at station number 1. The voltage E5 at tap 318 between theseresistors may be related to E; as follows:

Yet Tm is only a negligible fraction of R3 and the A substitution inEquation 36 of values derived in Equations 30, 31, 32, and 33, yields:

The resulting voltage E5, representing the temperature T2 (that is thetotal temperature at station 2) of Equation 29, is used to provide thecharge on the grid in section 422 of amplifier tube 420 through themedium of conductor 392.

Within the control box I6 is an oscillator tube 450 of the push pulltype. This oscillator tube is powered from the D. C. power source 60'and serves to control the polarity of transformer 466 according to therelative algebraic sign of the charges on the grids 452 and 454. Theprimary winding 456 of the transformer creates a field of alternatingpolarity. Secondary windings 412 and 462 power respectively thecomputing portion H and the controlling portion I3 of the control box.Tapped across secondar winding 412 is a potentiometer similar to thatillustrated in the embodiment of Figure 2, in series with a calibrationrheostat 396. The slide wire bar I8 is grounded. The cathode of theamplifier tube 422 of the controlling unit [3 is at the ground levelwith the slide wire 406. When the voltage E in lead 392 is at groundlevel, that is, the charge is neutral, this tube 422 conducts. The platein the side 424 of tube 420 is led suitably to the power source 60'through a resistor. Associated with this plate circuit is a line 426containing a condenser 42! which is led to a resistor grounded at 423 inparallel with a line 453 leading to the center tap in secondary winding462 of transformer 466. The terminals of coil 462 are led one to thegrid of phase discriminator tube 430 and the other to the grid of phasediscriminator tube 440. The plates of these latter mentioned tubes areled to a relay circuit comprising coils 43l, 432, 44!, 442, and relays436 and 446. interposed in this coil circuit are two condensers 434 and444 which will be described later. These solenoid coils are set up inopposed relation and when one overcomes the other, these coils serve toclose relays 43S and 446 as the case may be which throw onto the linemotor 80, grounded at 81'. This motor is an ordinary direct currentmachine and revolves in a direction depending upon which of its fieldcoils, either 84' or 86, happens to be energized. The relay and motorare conventional. As to the connections between the circuits of theamplifier tube and the discriminator tube during steady state conditionthe center tap 463 of secondary winding 462 is uncharged and the gridsof tubes 43!] and 446 alternately go positive-negative, thennegative-positive.

14 The effect will be that tube 436 will conduct for half a cycle andthen tube 446 will conduct for the next half cycle. Consider the halfcycle when tube 436 is conducted during the steady state condition. Afield will be created in coil 43! and also in coil 432, the formertending to close relay contact 436 and the latter tending to open relaycontact 446. The condenser 434 serves in the flywheel eiiect to maintaina fairly steady field intensity through these two coils underconsideration even during the half cycle when tube 430 is notconducting. On the other hand, during the next half cycle when tube 440conducts, the solenoid coil 44! is energized which tends to open relay436. Simultaneously coil 442 is energized which tends to close relaycontact 446. A condenser 444 in this circuit likewise tends to provideconstant flux through the two pertinent windings. The output of thetubes is the same during this situation because their capacities havebeen predetermined to be the same and the coils tend to counteract theeffect of one another and let the relay contacts remain unafiected.Accordingly, the motor 86 is idle. As to the active operation of theembodiment of Figure 3 the first change to be noted will be that voltageE5 in conductor 392 will go either above or below ground level and beginto carry an alternating charge. This condition will, of course, bebrought about by movement of the said lever 48' calling for more fueland accordingly causing the voltage E5 to be at variance with theground. For a practical illustration of the mechanics involved, let itbe assumed. that the instantaneous charge on the grid of tube 422 ispositive. This tube begins to conduct at an accelerated pace and causesless activity in tube 424 which conducts, by virtue of the condensercoupling with the tube 422, in a decreasing fashion with lowered output.The charge on the output side of condenser 42| .becomes less positiveand accordingly by means of line 426 the potential at center tap 463rises above ground level. If the instantaneous polarity of secondarywinding 462 happens at this time to be positive at terminal 466 andnegative at terminal 468, the voltage level will be at point 463actually more positively charged than when it was charged duringexistence of the normal ground level potential of the center tap. At alltimes that the terminal 466 is positive, tube 436 is the discriminatortube which is conducting, and the added potential to the grid will causetube 436 to conduct even more with the result that the field in thecoils 43! and 432 begins to strengthen. At this same time when centertap 462 becomes positive the potential at terminal 468 becomes lessnegative than it was and during the next half cycle will be lesspositive than what it is during the normal steady state condition. Theresult is that during this second half cycle when tube 446 isconducting, the coils 44! and 442 will be producing less of a fluxdensity and their field Will be altogether overcome by the strongerfields 43! and 432. Relay contacts 436 accordingly, will close, relaycontacts 443 will be enforcedly held open, and the motor windingappropriately selectively energized will cause motor 8 1' to revolve inone direction. The alternate condition which could have been chosenwould be that when the grid in amplifier tube 422 goes positive theterminal at 468 happens to he the positive terminal. Under suchcircumstances an opposite efifect will be experienced and the fieldcoils actuated by discriminator tube 443 will dominate, causing relay436 to open and the contact 446 to close thereby selectively energizingthe alternate winding for so effecting the motor 89 that it rotates inthe opposite direction. The motor 80', it will be recalled, operatesthrough the means of a rack and pinion to alter the fuel flow to theburner. Any change in fuel fiow will bring about a change in the voltagelevel at E5, which represents the temperature at station 2 and thesystem will be brought back into balanced condition.

In regard to Figure 4, a modification is shown for the embodiment ofFigure 3 just described whereby in place of a temperature sensitiveresistor there is used a thermometer bulb 22". This thermometer bulblocated in the inlet air passage as was the thermometer bulb of Figure 1and mounted on one end of a sealed conduit, causes by means of pressurechanges the actuation of a potentiometer and varies the tapped-offvoltage in direct relation to the temperature measured, that is, thehigher the temperature, the higher the voltage tapped off. The mode ofoperation for such thermometers was discussed in detail in connectionwith the first embodiment shown and operates in the same fashion as theinstant thermometer capsule or bulb arrangement.

In order that the current drawn by each successive potentiometer in theembodiments of Figures 3 and 4 does not seriously introduce an errorinto its preceding potentiometer, it may be found advantageous toarrange the resistances in proportion to one another such that thecurrent flowing in the conductor energized at the voltage E is of theorder of one ampere, for instance, whereas the current flowing in theconductor energized at voltage E1 of the order of one-tenth amperewhereas the current in the conductor energized at the voltage E2 is ofthe order of one-hundredth of an ampere and so on. It is alsocontemplated that in certain instances the potentiometers be formed ofvarying resistors which will readily compensate for the additionalcurrent carried by it for the succeeding potentiometers.

The embodiments just described have certain features in common with oneanother. The positionable members comprising the rack and pinion, motorshaft, and motor rotor are adapted accurately to adjust the valving inthe restricted fuel path which ultimately determines the rate of flow offuel allowed for consumption by the burner. So long as the drive intothe initial section of the amplifier device remains at the zero orground level the disposition of the valving remains unchanged.Fluctuations in the flow pressures of the intake air and discharge gasesas well as fluctuations in the intake air temperature are compensatedfor by the control apparatus which properly re-positions the valving inthe fuel flow control. While temperature sensitive means are used, suchmeans only contribute to the determination of the discharge temperatureand paradoxically enough, are located in the inlet air passages. If thequality of fuel used is changed such that the heat output per unitquantity is changed, the instant control apparatus senses the dischargetemperature change and self-compensates the fuel flow rate. Moisturecontent of the air supplied may be changed whereupon automaticcompensation is eifected. Thus changes in the actual quality of the fueland air supplied do not necessitate a recalibration of the instantdevice since the thermal level is automatically controlled bycompensated fuel rate of flow, Inasmuch as the variables just mentionedhave been interrelated by well known and fundamental thermodynamic lawsthe combustion temperature will be automatically maintained at aconstant value by an inferential method. Once, however, is the manuallyoperable slider changed as to its position so as to vary the inputvoltage to the control apparatus, then the resultin electrical signalarising out of the condition that the voltage equilibrium of the systemhas been changed into an unmatched state is impressed upon the amplifierand causes the fuel metering motor to readjust the position of thevalving and change the combustion temperature by an appropriate amount.So soon as the combustion temperature changes, then according to thecontrol equation the various temperatures and pressures are registeredwhereby the positionable potentiometer sliders are operated to match thenew voltage setting inaugurated by the manually operable temperaturesetting lever. The control equations of the embodiments of the inventiondescribed as has been pointed out, involve the same variables except ina slightly diiferent fashion. These expressions, however, have beeninterrelated with the control apparatus so as to yield a suitableelectrical signal to which the amplifier is responsive and to bring thesystem back into a state of equilibrium. For any assigned combustiontemperature, the Tsct is equalled by the actual T2 on the downstreamside of the burner owing to the automatic positioning tendency of thepotentiometers. That is to say, so long as the respective expressionsset forth yield constant values:

the actual temperature maintained equals the discharge temperaturedesired. In the first embodiment the fuel control motor was controlledin response to demands of the amplifier by means of one variable windingfor which the energization could be controlled to varying degrees. Inthe second and third embodiments shown the metering motor was controlledby two windings which were selectively energized by the amplifier in analternative fashion. That is to say, when the one winding was energizedthe other winding was deenergized altogether.

By way of further summary, it may be said that the last embodiment showndiiiered from the second embodiment in the manner by which intake airtemperature was employed to vary the matching voltages in the electricalsystem of the control apparatus.

It will thus be seen that there has been disclosed suitable apparatusfor determining coinbustion temperatures which is not subject to thepoor response characteristics of a thermocouple or other metaltemperature-sensing device and that an apparatus has been disclosedwhich is further not effected by the errors of radiation, conduction,and oxidization.

While suitable physical embodiments for the purpose of disclosing theinvention has been illustrated in the accompanying drawings andhereinafter described, it is to be understood that the invention is notlimited to the particular embodiments so illustrated and described butthat such changes in the size, shape, and arrangements of the variousparts and their particular functionszmay:berexertedtoasuchaas will-occurto thosesskilled intheart.

The invention "now "having been described so that othersrskilled intheart may clearly understand the same, the claims are set forth to follow.By the :term air used therein is meant any suitablecombustion-supporting medium and by fuel is meantany liquid, gaseous,crushed-or powderedfuel appropriatefor use in burners.

We claim:

v1. In a regulative combustion system inferentially determinative-ofcombustion temperatures irrespective of the initial quality of thefluids supplied and characterized by a burner, means providing a pathfor the flowjof air to the burner, meansproviding a path for the flow ofenergy gases discharged from the burner, means providing a path for'theflow of. fuel to the burner, and a metering element adjustable'to varythe rate of flow of fuel to the burner: the combination comprising avoltage divider including an indicator element adjustable to positionsindicative of specific discharge temperatures-of the energy gases,pluralized voltage divider means, :a bridge circuit including saidvoltage divider and said voltage divider means, said voltagedividermeans comprising first, second, third, fourth, andfifth voltagedividers, each including an adjustable contact and being coupled withone another in predetermined sequence ina manner such that a majority ofthe dividers are each coupled across the rtion of the preceding dividerselected by its contact and at least one divider is coupled across afixed length of the preceding divider, said first voltage dividerincluding a contact adjustablein accordance with the temperature of the.air flowing to the burner effective to adjust the bridge circuit, saidsecond voltage divider including a contact adjustable-in accordanc withthe force differential created by the static and total pressures of theair flowing to the burner acting predeterminedly .in oppositiontooneanother and eii'ective .to adjust the bridge circuit, saidthirdvoltage divider including a contact adjustable in accordance with theforce difierential createdby the static and totalpressures of the energygas from the burner acting predeten minedly in opposition to one anotherandefiective to adjust the bridge circuit, said fourth voltage dividerincluding a contactadjustable in accordance with the static pressure .01the air flowing to the'burner effective to adjust the bridge circuit,and said fifth voltage divider includinga contact adjustable inaccordance with the static pressure of the energy gas from the burnereffective to adjust the bridge circuit, and means responsive to thevalue of unbalance potential existing in the bridge circuit foradjusting an adjustable element above-named.

2.In a regulativecombustion system inferentially determinative ofcombustion temperatures irrespective of the initial quality .of .thefluids supplied and characterized'by a burner, means providing a path'for'the'fiow chair to the burner. means providing "a path'i'or'the flowof energy gases discharged from the burner, means, providing-a pathfortheflow ofjiuel tothe burner, and a metering element adjustable tovary the 'rate of flow of fuel to the burner: the combinationcom-prising a voltage divider including an in-' dicator elementadjustable to positions indicative of specific discharge temperatures ofthe energy gases, pluraiizedvoltage divider'means',-a bridge circuitincluding ;.said voltage divider and ;said

voltagedivider means. saidvoltaae:dividermeans comprising first, second,third, Iourth, and :flfth volt ge dividers, each including an adjustablecontact and being coupled with one anotherin predetermined sequence inamanner such that armajority of the dividers are each coupled across theportion of the preceding divider selected by its contact and atleast'one divider iscoupled across a fixed length of Jtheprecedingdivider, said first voltage divider including a contact ad-- justable inaccordance with the temperatureof the airflowing to the burnereffectiveto adjust the bridge circuit, said second voltage dividerincluding a contact adjustable in accordance with the force difierentialcreated'by .the static and total pressures of the air flowing totheburner acting predeterminedly in oppositionito-ione another andefi'ective to adjust the bridge circuit, said third voltage dividerincluding a contact adjustable in accordance with the force difierentialcreated by the static and totalpressures of the energy gas from theburner acting predeterminedly in opposition to one'another and efiectiveto adjust the bridge circuit, said fourth voltage divider including acontact adjustable in .accordance with the static pressure of the airflowing to the burner effective to adjust the bridge circuit, and saidfifth voltage divider including acontact adjustable in accordance withthe static pressure of the energy gas from the burner'effective toadjust the bridgecircuit, and mean responsive to the value oi unbalancepotential existing in the bridge circuit for adjusting an adjustableelement above-named.

3. In .a regulative combustionsysteminferentially determinative ofcombustion temperatures irrespective of the initial qualityof the fluidssupplied and characterized by a, burner, means providing a path for theflow of air to thezburner, means providing a path for th-eflowof energygases discharged from-theburner, means providing a path for the flowoffucl to the burner, and a metering element adjustable to vary-the rateof flow of fuel to the burner: the combination comprising a voltagedivider including ,an indicator elementadjustable topositions indicativeof specific discharge temperaturesof the energy gases, pluralized.voltage divider means, a bridgecircuit including saidvoltagedivider andsaid voltage divider means, said voltage divider means comprising first,second,andthirdvoltagc dividers, each including an adjustable contactand being coupled with one anotherin predetermined sequence in amannersuch that :-a majorityof the dividers are each coupledacrosstheportion of the preceding divider selected'by its contact,.saidfirst-voltage dividerincluding a contact adjustable in accordance withthetemperature of the air flcwingto the burner effective to adjust thebridge circuit,-.said second voltage-db vider including a contactadjustable in accordance with the force differential created .by thestatic and total pressureso'f the :air flowing-to the burner actingpredeterminedly in oppOsit-ion to one another and effective to adjustthe bridge circuit, and-said third voltage divider including a contactadjustable in accordance with the force differential created bythevstatic and'totai pressures of the energy gas from, the burnertacting predeterminedly in opposition-toone another and "effective -toadjust the bridge circuit-and means responsiveto the val-ue-o'tunbalandep tential existing in the bridge-circuit vfor adjusting an adjustableelement above-named.

4. In a combustion apparatus-for aifueiriired burner system"characterized by fuel and iflhfine 19 lets, an energy gas discharge,and a fuel flow controlling mechanism having an adjustable element, thecombination with voltage divider means including an adjustable elementsettable to adjusted positions indicative of changed combustiontemperatures established in the burner system, pluralized voltagedivider means, bridge circuit means including both divider meansaforesaid, and means responsive to unbalance potentials in the bridgecircuit to adjust the appropriate adjustable element above-mentioned,said pluralized divider means having at least first, second and thirdvoltage dividers including first, second, and third adjustable contactsrespective ly interrelated electrically in sequence such that a majorityof the dividers are each coupled across the portion of the precedingdivider selected by its contact, of actuating means for adjusting saidfirst, second, and third adjustable contacts consistlng of meansresponsive to inlet air static, pressure (P51) means responsive to inletair total pressure (Pm) means responsive to inlet air temperature (T1),means responsive to energy gas v total pressure (Pm), and meansresponsive to energy gas static pressure (PS2), said actuating meansbeing precalibrated for effecting the above-described adjustmentswhereby the value of the established combustion temperature in theburner system is yielded by the expression:

Pd m- 02) P tl" sl) 5. In a combustion apparatus for a fuel fired burnersystem characterized by fuel and air inlets, an energy gas discharge,and a fuel flow controlling mechanism having an adjustable element, thecombination with voltage divider means including an adjustable elementsettable to adjusted positions indicative of changed combustiontemperatures established in the burner system, pluralized voltagedivider means, bridge circuit means including both divider meansaforesaid, and means responsive to unbalance potentials in the bridgecircuit to adjust the appropriate adjustable element above-mentioned,said pluralized divider means having at least first, second and thirdvoltage dividers including first, second, and third adjustable contactsrespectively, interrelated electrically in sequence such that a majorityof the dividers are each coupled across the portion of the precedingdivider selected by its contact, of actuating means for adjusting saidfirst, second, and third adjustable contacts consisting of meansresponsive to inlet air static, pressure (Psl), means responsive toinlet air total pressure (Pu), means responsive to inlet air temperature(T1), means responsive to energy gas total pressure (Pm) and meansresponsive to energy gas static pressure (PS2), said actuating meansbeing precalibrated for effecting the above-described adjustmentswhereby the value of the established combustion temperature in theburner system is yielded by the expression:

let i P a ut= 1 51 z1] 42- 12] 6. Means for automatically controllingthe rotative position of a fuel metering motor in an operatingcombustion system characterized by a burner supplied with the meteredfuel and having means providing for a supply of intake air and fordischarge of the energy gases, said fuel metering motor having aplurality of windings energizable to position the motor; said meanscomprising means including an amplifier device 20 responsive toelectrical signals for controlling the energization of at least one ofsaid windings to change the respective metering rate position of themotor, and means including an electrical system in a state of voltagebalance comprising operator operated voltage divider means for changingthe voltage level to be maintained in the system to adifferent levelthereby introducing a state of unbalance in the system, and pluralizedvoltage divider means connected to said operator operated divider meansfor matching the new voltage level and restoring balance to the system,said pluralized divider means beingadapted to emit signals to theamplifier device for appropriately changing the metering rate to adifferent rate only so long as unbalance exists in the system and havingfirst, second, third, fourth, and fifth voltage dividers electricallyinterrelated in-a predetermined sequence such that a majority of thedividers are each coupled across the portion of the preceding dividerselected by its contact and at least one divider is coupled across afixed length of the pre ceding divider, said first voltage dividerincluding an element adjustable in accordance with the temperature ofthe intake air to the burner, said second voltage divider including anelement adjustable in accordance with an existing force differentialcreated by static and total pressures of the intake air acting inopposition to one another according to a predetermined relationship,said third voltage dividerincluding an element adjustable in accordancewith an existing force differential created by static and totalpressures of the energy gas acting in opposition to one anotheraccording to a predetermined relationship, said fourth voltage dividerincluding an element adjustable in accordance with one of the static andtotal pressures of the intake air to the burner, and said fifth voltagedivider in-- cluding an element adjustable in accordance with one of thestatic and total pressures of the energy gas from the burner.

' 7. Means for automatically controlling the rotative position of a fuelmetering motor in an operating combustion system characterized, by aburner supplied with the metered fuel, said fuel metering motor having aplurality of windings energizable to position the motor; said meanscomprising means including an amplifier device responsive to electricalsignals for controlling the energization of at least one of saidwindings to change the respective metering rate position of the motor,and means including an electrical system in a state of voltage balancecomprising operator operated voltage divider means for changing thevoltage level to be maintained in the system to a different levelthereby introducing a state of unbalance in the system, and pluralizedvoltage divider means connected to said operator operated divider meansfor matching the new voltage level and restoring balance to the system,said pluralized divider means being adapted to emit signals to theamplifier device for passages across a fixed length of the precedingdivider, said first voltage divider including an element adjustable inaccordance with the temperature of the intake air to the burner, saidsecond voltage divider including an element adjustable in accordancewith an existing force diiferential created by staticand total pressuresof the intake air acting in opposition to one another according to apredetermined relationship, said third'voltage divider including anelement ad.- justable in accordance with an existing force difierentialcreated by static and total pressures of the energy gas acting inopposition to oneanother according to "a predetermined relationship,said fourth voltage divider including'an element adjustable inaccordance with one of the static and total pressures of the intake airto the burner, and said fifth voltage divider including an elementadjustable in accordance with one oi the static and total pressures ofthe energy gas from the burner.

8. Means for automatically controlling the rotative position of a fuelmetering motor in an operating combustion system characterized by aburner supplied with the metered fuel and having means providing for asupply of intake air and for discharge of the energy gases, said fuelmetering motor having a plurality of windings energizable to positionthe motor; said means comprising means including an amplifier deviceresponsive to electrical signals for controlling the 'energization ofsaid windings to change the respective metering rate position of themotor, and means including an electrical system in a state of voltagebalance comprising operator operated voltage divider means for changingthe voltage level to be maintained in the system to a different levelthereby introducing a state of unbalance in the system, and pluralizedvoltage divider means connected to said operator operated dividermeans'for matching the new voltage level and restoring balance to thesystem, said pluralized divider means being adapted to emit signals tothe amplifier device for effecting a variance in the overall characterof the energization maintained on a certain winding to cause appropriatechange in the metering rate to a difierent rate only so long asunbalance eX- ists in the system and having a plurality of voltagedividers electrically interrelated in sequence such that a majority ofthe dividers are each. coupled across the portion of the precedingdivider selected by its contact and at least one divider is coupledacross a fixed length of the preceding divider, said pluralitycomprising a first voltage divider including an element adjustable inaccordance with the temperature of the intake air to the burner, asecond voltage divider including an element adjustable in accordancewith an existing force differential created by static and totalpressures of the intake air acting in opposition to one anotheraccording to a predetermined relationshipyand a third voltage dividerincluding an element adjustable in accordance with an existing forcedifferential created by static and total pressures of the energy gasacting in opposition to one another according to a predeterminedrelationship.

9. Means-forautomatically controlling the rotative position of a fuelmetering motor in an operating combustion system characterized by aburner supplied with the metered fuel and having meanssprovidingfor asupply of intake airand for discharge oflthe: energy gasespsaid fuelmetering motor having a plurality of windings energizable to positionthe motor; said'means comprising means including an amplifier deviceresponsive to electrical signals for controlling th energizetion of saidwindings to change the respective metering rate position of the motor,and means including an .electricalsystem in a state of *volt age balancecomprising operator operated'voltage divider means for changing thevoltage level to be maintained in the. system to a different levelthereby introducing a state of unbalance in the system, andpluralizedvoltage divider means connected to the operator operateddivider means for matching the new voltage level and-restoring balanceto the system, said pluralizedtvoltage divider means being adapted toemit signals to the amplifier device for efiecting-a variance-inthe'overall character of the energization main!- tained on a certainwindingto cause appropriate change in the metering rate to a differentrate only so long as unbalance exists in the system and having first,second, third, fourth, and fifth volt-' age dividers electricallyinterrelated in a-predetermined sequence such that a majority of thedi-' viders are each coupled across the portion of the preceding dividerselected by its contact andat least one divideris coupled across a fixedportion of'the preceding divider, said first voltage divider includingan element adjustable in accordance with the temperature of the intakeair to the burner, said second voltage divider including an elementadjustable in accordance with the magnitu'de'of the velocity pressure ofthe intake air, said third voltage divider including an elementadjustable in accordance with the magnitude-of the velocity pressure ofthe energy gas, said fourth voltage divider including an elementadjustable in accordance with the first power 'of the static pressure ofthe intake air to the burner, and said fifth voltage divider includingan element adjustable in accordance with the first power of the staticpressure of the energy gas from the burner.

'10. Means for automatically controlling themtative' position of a fuelmetering motorin an operating combustion system characterized by aburner supplied with the metered fuel and having means providing for asupply of intake air and for discharge of the energy gases, saidfuelmetering motor having a plurality of windings energizable toposition the motor; said means comprising means including an amplifierdevice responsive to electrical signals for controlling the energizationof at least one of said windingsto change the respective metering rateposition of the motor, and means including an electrical system in astate of voltage balance comprising operator operated voltage dividermeans for changing the voltage level to be maintained in the system to adifi'erent level thereby "introducing a state of unbalance in thesystem, and pluralized voltage divider means connected to the operatoroperated divider means formatching the new voltage level and restoringbalance to the system, said pluralized divider means being adapted toemit signals to the amplifier device for appropriately changing themetering rate to a difierent rate only so long as unbalance exists inthe system and having a plurality of voltage dividers electricallyinterrelated in sequence such that a majority of the dividers are eachcoupled across the portion ofthe preceding divider selected by itscontact and at least one divider'is coupled'across a fixed length of theprece.dingdivider, said plurality *comprisinga first voltage dividerincluding an element adjustable in accordance with the temperature ofthe intake air to the burner, a second voltage divider including anelement adjustable in accordance with an existing force differentialcreated by static and total pressures of the intake air acting inopposition to one another according to a predetermined relationship, anda third voltage divider including an element adjustable in accordancewith an existing force difierential created by static and totalpressures of the energy gas acting in opposition to one anotheraccording to a predetermined relationship. 7

I 11. In a regulated combustion system characterized by a burner, asupply of fuel for eventual introduction into the burner, means forminga restricted fuel fiow path for use in varying the flow rate of the fuelallowed to be introduced into the burner, means forming a path for theflow of air to the burner, and means forming a path for the flow of theproducts of combustion discharged by the burner: the combination withpositionable members, valving in the restricted fuel path connected formovement with one of the positionable members, a voltage divider meansadapted for graduation in terms of combustion temperature and includingone of said positionable members having positions indicative ofgraduated temperature, pluralized voltage divider means, a bridgecircuit including both divider means aforesaid, and means responsive tounbalance potential existing in the bridge circuit to position one saidpositionable member, said pluralized voltage divider means comprisingfirst, second, third, fourth, and fifth voltage dividers includingfirst, second, third, fourth, and fifth adjustable elementsrespectively, said voltage dividers being interrelated electrically in asequence in a manner such that a majority of the dividers are eachcoupled across the efiective portion of the preceding divider selectedby its adjustable element and at least one divider is coupled acrosssome portion of the preceding divider unadjusted by its adjustableelement, of means for adjusting the respective adjustable elements ofthe abovenamed voltage dividers including means responsive to the flowof air, to the burner, means responsive to the temperature of the air tothe burner, and means responsive to the flow of products of combustiondischarged by the burner, the above described responsive means being fora given combustion temperature interrelated and arranged at all times asto satisfy the following expression:

where T1=temperature of air to the burner Ps1=static pressure of the airto the burner Pu=total pressure of the air to the burner Piz==staticpressure of the products of combustion Pzz=total pressure of theproducts of combustion 12. In a regulated combustion systemcharacterized by a burner, a supply of fuel for eventual introductioninto the burner, means forming a restricted fuel flow path for use invarying the flow rate of the fuel allowed to be introduced into theburner, means forming a path for the flow of air to the burner, andmeans forming a path for the flow of the products of combustiondischarged by the burner: the combination with positionable members,valving in the restricted fuel path connected for movement with one ofthe 24 positionable members, a voltage divider mean adapted forgraduation in terms of combustion temperature and including one of saidpositionable ,members having positions indicative of graduatedtemperature, pluralized voltage divider means, a bridge circuitincluding both divider means aforesaid, and means responsive tounbalance potential existing in the bridge circuit to position one saidpositionable member, said pluralized voltage divider means comprisingfirst, second, third, fourth, and fifth voltage dividers includingfirst, second, third, fourth, and fifth adjustable elementsrespectively, said voltage dividers being interrelated electrically in asequence in a manner such that a majority of the dividers are eachcoupled across the effective portion of the preceding divider selectedby its adjustable element and at least one divider is coupled acrosssome portion of the preceding divider unadjusted by its adjustableelement, of means for adjusting the respective adjustable elements ofthe abovenamed voltage dividers including means responsive to the flowof air, to the burner, means responsive to the temperature of the air tothe burner, and means responsive to the flow of products of combustiondischarged by the burner, the above described responsive means being fora given combustion temperature interrelated and arranged at all times asto satisfy the following expression:

where Ti=temperature of air to the burner Ps1=static pressure of the airto the burner Pn=total pressure of the air to the burner Psz=staticpressure of the products of combustion Prz=total pressure of theproducts of combustion 13. Means for automatically controlling therotative position of a fuel metering motor in an operating combustionsystem characterized by a burner supplied with the metered fuel andhaving means providing for a supply of intake air and for discharge ofthe energy gases, said fuel metering motor having a plurality ofwindings energizable to position the motor; said means comprising meansincluding an amplifier device responsive to electrical signals forcontrolling the energization of at least one of said windings to changethe respective metering rate position of the motor, and means includingan electrical system in a state of voltage balance comprising operatoroperated voltage divider means for changing the voltage level to bemaintained in the system to a different level thereby introducing astate of unbalance in the system, and pluralized divider means formatching the new voltage level and restoring balance to the system, saidpositionable means being adapted to emit signals to the amplifier devicefor appropriately changing the metering rate to a different rate only solong as unbalance exists in the system and having first, second, andthird voltage dividers electrically interrelated in a predeterminedsequence such that at least a majority of the dividers are each coupledacross the portion of the preceding divider selected by its contact,said first divider including a contact adjustable in accordance with thetemperature of the intake air to the burner, said second dividerincluding a contact adjustable in accordance with an existing forcedifferential created by the static and total pressures of the intake airacting in opposition to one am other. accordingto a predeterminedrelationship, andsaid third divider including a'contact, adjustable-inaccordance withan existing force differential created by the static andtotal pressures of the energy gas acting in opposition to one anotheraccording to a predetermined relationship.

14. A systemrfor controlling the rate of fuel flow to the combustionzone of a burner, theresulting combustion temperature of which is to bemaintained uniformly at predetermined values by adjustment of fuel flowwithout recourse to the basis of actual measurement of combustiontemperatures but rather in accordance with the respective magnitudes ofother variable quantities involved in the combustion process, saidburner having an adjustable fuel control: comprising, a plurality ofvoltage dividers each in: cluding an adjustable contact and beinginterrelated consecutively with one another in a manner such that amajority of the dividers are each coupled across the portion of thepreceding divider selected by its contact and at least one divider iscoupled across a fixed length of the preceding divider, means foradjusting the contact of a first of said divider plurality in accordancewith variations of a first of said other variable quantities, means foradjusting the contact of a second of said divider plurality inaccordance with variations of a second of said other variablequantities, means for adjusting the contact of a third of said dividerplurality in accordance with variations of a third of said othervariable quantities, means for adjusting the contact of a fourth of saiddivider plurality in accordance with variations of a fourth of saidother variable quantities, means for adjusting the contact of a fifth ofsaid divider plurality in accordance with variations of a fifth ofsaidother variable quantities, a sixth voltage divider including a contactsettable to a position representative of the combustion temperature in;the burner, a bridge circuit including said sixth voltagedivider andsaid divider plurality, and means responsive to an unbalance of saidbridge circuit for adjusting the fuel flow control of the burners.

15. A system for controlling the rate of fuel flow to the combustionzone of a burner, the resulting combustion temperature of which is to bemaintained uniformly at predetermined values by adjustment of fuel flowwithout recourse to the basis of actual measurement of combustiontemperatures but rather in accordance with the respective magnitudes ofother variable quantities involved in the combustion process, saidburner having an adjustable fuel control: comprising, a plurality ofvoltage dividers each including an adjustable contact and beinginterrelated consecutively with one another in a manner such that amajority of the dividers are each coupled across the portion of thepreceding divider selected by its contact and at least one divider iscoupled across a fixed length of the preceding divider, contactadjusting means for the divider plurality including means for adjustingthe contact of a first of said divider pluralityin accordance withvariations of a first of said other variable quantities, means foradjusting the contact of a second of said divider plurality inaccordance wtih variations of a pressure-diiferential aiforded by saidother variable quantities, and means for adjusting the contact of athird of said divider plurality in accordance with variations of apressure-differential afiorded by said other variable quantities, afourth voltage divider including a, contact settable to a positionrepre: sentative of the combustion temperature in the: burner, a bridge.circuit including said fourth. voltage divider and said dividerplurality, and means responsive to an unbalance of said bridge circuitfor adjusting the fuel flow control of the, burner;

16. A system for controlling the rate of fuel flow to the combustionzone of a burner, there, sulting combustion temperature of which is to,be maintained uniformly at predetermined values by adjustment of fuelflow without recourse to the basis of actual measurement of combustiontemperatures but rather in accordance withthe respective magnitudes ofother variable quantities involved in the combustion process, saidburner having an adjustable fuel control: comprising, a plurality ofvoltage dividers cachineluding an adjustable contact and being inter!related consecutively with one another in a man-- ner such that amajority of the dividers are each. coupled across the portion of thepreceding divider selected by its contact and at least one.

divider is coupled across a fixed length of the preceding divider,contact adjusting means for the divider plurality including means foradjusting the contact of a first of said divider plurality in accordancewith variations of a first of said other variable quantities, means foradjusting the contact of a second of said divider plurality inaccordance with variations of a second of said other variable quantitiesand means for adjusting the contact of a third of said divider pluralityin accordance with variations of a third of said other variablequantities, a fourth voltage divider including a contact settable to aposition representative of the combustion temperature in the burner, abridge circuit including said fourth voltage divider and said dividerplurality, and means responsive to an unbalance of said bridge circuitfor adjusting the fuel flow control of the burner.

1'7. In a regulative combustion system inferentially determinative ofcombustion temperatures irrespective of the initial quality of thefluids supplied and characterized by a burner, means providing a pathfor the flow of air to the burner, means providing a path for the flowof energy gases discharged from the burner, means providing a path forthe flow of fuel to the burner, and a metering element adjustable tovary the rate of flow of fuel to the burner: the combination comprisinga voltage divider including an indicator element adjustable to positionsindicative of specific discharge temperatures of the energy gases,pluralized voltage divider means, a bridge circuit including saidvoltage divider and said voltage divider means, said voltage dividermeans comprising first, second, and third voltage dividers each havingcoupling means to couple it in the divider means with the other dividersin predetermined sequence in a manner such that a majority of thedividers are each coupled across the portion of the preceding dividerselected by its contact, said coupling means comprising grid controlledmeans between at least two said adjacent voltage dividers and having thecontrol grid thereof controlled by the preceding one of the two saidadjacent voltage dividers and providing an anode-cathode path includedin series with the successive one of the two said adjacent voltagedividers for controlling the energization of the latter in controlleddependence upon said control grid, said first voltage divider includingan adjustable member adjusted in accordance with the temperature of theair flowing to the burner efiective to adjust the bridge circuit, saidsecond voltage divider including a contact adjustable in accordance withthe force difierential created by the static and total pressures of theair flowing to the burner acting predeterminedly in opposition to oneanother and effective to adjust the bridge circuit, and said thirdvoltage divider including a contact adjustable in accordance with theforce differential created by the static and total pressures of theenergy gas from the burner acting predeterminedly in opposition to oneanother and effective to adjust the bridge circuit, and means responsiveto the value of unbalanced potential existing in the bridge circuit foradjusting an adjustable element above-named.

18. Means for automatically controlling the rotative position of a fuelmetering motor in an operating combustion system characterized by aburner supplied with the metered fuel, said fuel metering motor having aplurality of windings energizable to position the motor; said meanscomprising means including an amplifier device responsive to electricalsignals for controlling the energization of at least one of saidwindings to change the respective metering rate position of the motor,and means including an electrical system in a state of voltage balancecomprising operator operated voltage divider means for changing thevoltage level to be maintained in the system to a different levelthereby introducing a state of unbalance in the system, and pluralizedvoltage divider means connected to said operator operated divider meansfor matching the new voltage level and restoring balance to the system,said pluralized divider means being adapted to emit signals to theamplifier device for effecting-energization of at least one of saidmotor windings to change appropriately the metering rate to a difierentrate only so long as unbalance exists in the system and having first,second, third, fourth, and fifth voltage dividers having coupling meanselectrically interrelating them in a predetermined sequence such that amajority of the dividers are each coupled across the portion of thepreceding divider selected by its contact and at least one divider iscoupled across a fixed length of the preceding divider, said couplingmeans comprising grid controlled means between at least two saidadjacent voltage dividers and having the control grid thereof controlledby the preceding one of the two said adjacent voltage dividers andproviding an anodecathode path included in series with the successiveone of the two said adjacent voltage dividers for controlling theenergization of the latter in controlled dependence upon said con trolgrid, said first voltage divider including an element adjustable inaccordance with the tem perature of the intake air to the burner, saidsecond voltage divider including an element adjustable in accordancewith an existing force differential created by static and totalpressures of the intake air acting in opposition to one anotheraccording to a predetermined relationship, said third voltage dividerincluding an element adjustable in accordance with an existing forcedifferential created by static and total pressures of the energy gasacting in opposition to one another according to a predeterminedrelationship, said fourth voltage divider including an elementadjustable in accordance with one of the static and total pressures ofthe intake air to the burner. and said fifth voltage divider includingan element adjustable in accordance with one of the static and totalpressures of the energy gas from the burner.

DAVID M. BQRDEN. PAUL T. NIMS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,455,633 Lundgard May 15, 19231,576,754 McLean Mar. 16, 1926 1,680,026 McLean -Aug. 7, 1928 2,323,180Junkins June 29, 1943 2,337,851 Junkins Dec. 28, 1943 2,414,314 MachletJan. 14, 1947

